Magnetically Induced Spin-Reversal Transitions in Impurity Hop Conduction inn-Type Germanium

Abstract

At high magnetic fields (45-146 kG) the magnetoresistance $\frac{\rho }{{\rho }_0}$ of hop conduction in $n$-type germanium is found to have a temperature dependence which increases with field strength. It is shown that phononassisted tunneling with reversals of spins of electrons while they make interdonor transitions can account for this effect. Spin reversals are caused by strong coupling of phonon shear waves with spins of electrons in donor ground states in the presence of the magnetic field. An expression for the probability of the interdonor transition with spin flip is obtained by modifying the ordinary spin-lattice relaxation theory to apply to a two-donor system. The modification follows the theory for phonon-assisted spin-conserving electron tunneling between donors.